swallert



Feb. 21, 1956 s. A. SWALLERT PNEUMATIC SPIKE EXTRACTOR Filed Sept. 16, 1953 2 Sheets-Sheet 1.

Fig.2

5. A Sw/MAERT Feb. 21, 1956 s. A. SWALLERT 2,735,649

PNEUMATIC SPIKE EXTRACTOR Filed Sept.- 16, 1953 2 Sheets-Sheet 2 Fig.3 1? 16 14 I N vavrok: S. A. s w; L a RT United States Patent PNEUMATIC SPIKE EXTRACTOR Sven Arild Swallrt', Lidingo, Sweden Application September 16, 1953, Serial No. 380,402

3 Claims. (Cl. 254-18) The invention relates to a pneumatic spike extractor of the type in which two jaws are pivotably mounted on the outer end of a rod fixed to a pressure-air operated piston. Said piston is enclosed in a cylinder provided with devices for alternately connecting the chambers on both sides of the piston with a source of pressure air. A locking member is generally arranged to lock the jaws in a position gripping the head of a nail, when the piston rod is in its outer position.

The object of the invention is to provide an improved jaw Construction and improved locking means by which the nail to be extracted may be held in a secure grip.

According to the invention, means for locking the jaws in open and closed position consist of a double-armed lever pivotably mounted on the piston rod and'provided with locking members on both sides of its pivot. In dependence on the position of the lever, said locking members are arranged to engage corresponding locking members on the jaws to lock the jaws in gripping and open position respectively, and the lever is arranged to be rocked between its two locking positions by engaging fixed abutrnents near the two end positions of the piston rod. Said locking members on the lever and the jaws may consist of hooks or knobs and corresponding recesses. In a preferred embodiment the lever has hooks and the jaws have corresponding recesses but it is evident that the reverse may be the case. U

The device according to the invention will be described more in detail in the following with reference to the accompanying drawings which show a preferred embodiment of a spike extractor.

In the drawings:

Figure 1 shows the apparatus in longitudinal section with the jaws in a retracted position.

Figure 2 shows a side view of the lower part of the apparatus, as seen at an angle of 90 in relation to Figure 1.

Figure 3 is a longitudinal section of the apparatus and shows the piston rod advanced against a nail head, while the jaws are moving towards each other to grip the head of the nail.

Figure 4 is a longitudinal section through the lower portion of the apparatus and shows the piston rod in its outermost position, where a hook locks the jaws in the position gripping the head of the nail.

In the drawings, 5 indicates a cylinder mounted between an upper end plate 6 provided with a handle 7 and a lower end plate s. The two plates 6 and 8 are held together by bolts 9. A plunger 10 is movable in the cylinder and its piston rod 11 projects through a central opening in the lower plate 8. A pipe socket 12 mounted on the handle 7 is adapted to be connected to a source of pressure air for supplying pressure air to either side of the plunger 10 through a channel system.

A channel 13 leads from the pipe socket 12 to a boring in the opposite end of the handle 7. A slidable valve member 14 consisting of two disks connected by an intermediate element of smaller diameter is inserted in the boring and normally held in its outermost position by a spring 15 placed between the bottom of the boring and the inner end of said valve member. The movement of the valve member 14 in the direction outwardly is limited by a sleeve 16 screwed into the outer end of the boring. A rod 17 fixed to the outer end of the valve member 14 passes with clearance through the sleeve 16 and carries a knob 18 at its outer end.

In Figure 1, the knob 18 is not operated and ceasequently the valve member is in its outermost position in which the channel 13 communicates with a channel 19 leading to the lower end of the cylinder 5 over the annular space formed between the two valve disks in the valve casing. Thus, when the pipe" 12 is connected to a pressure air conduit the pressure air will act upon the underside of the plunger 10 and move the plunger into its uppermost position. The air in the chamber above the plunger 10 escapes through a channel 20' and a narrow channel 21 connecting the bottom of the valve casing with the atmosphere. When the valve member is moved inwardly by depressing the knob. 18, the channel 13 is instead connected to the channel 20 over the annular space bet-ween the valve disks and pressure air is supplied to the upper side of the plunger 10. At the same time the air escapes from/the chamber below the plunger through the channel 19 which now e'nds outside the valve member 14.

The lower end or the pistonrod ii is formed as a fork in which two approximately hemicir'cular disks 22 carrying the jaws 23 are mounted on a common pivot pin 24 inserted through the centre of the disk circles. Each jaw is constructed so that its outer curvature constitutes a continuation of the periphery of the disk. Each jaw has a thickness equal to the thickness of both disks (see Figure 2) so that a projecting edge 25 is formed serving to limit the rotation of adjacent disk. The end of each disk opposite to its jaw is provided with a projection 26, the purpose of which will be explained hereinafter. Further, each disk 22 has two notches 27 and 28 (Figures 3 and 4) provided at a distance from each other in the upper, circular edge of the disk.

A locking member 29 is placed above the disks 22 and is also pivotably mounted (on a pin 30) in the forkshaped end of the piston rod 11. Said member 29 consists of a double-armed lever which is curved to partly surround the upper portion of the disks at some distance. On its underside the lever has projecting books 31, 32 adapted to engage the notches in the disks in certain positions. A spring 33 is inserted in an axial boring in the piston rod 11 and its outer end carries a plunger 34 arranged to press against a cam 35 provided on the upper side of the lever 29 just above the pivot pin 30. Thus, the locking member may be rocked between two end positions and the spring-actuated plunger 34 contributes in holding the locking member in its adjusted position by engaging the cam 35.

The plate 8 has a cylindrical sleeve 36 at its bottom side. Said sleeve contains a packing box 37 surrounding the piston rod 11. A cylindrical casing 38 is fixed to the sleeve 36 and projects downwardly to surround the piston rod and the jaws. The lower end of this casing 38 is adapted to rest on the object from which the nail is to be extracted. The casing 38 has an opening 39 at its bottom, through which the jaws may project. The cylindrical portion of the casing 38 has two diametrically opposed, longitudinal slots 40, 41 (see also Figure 2) to receive the projections 26 from the disks 22 and an extended end of the locking member 29. Larger openings 42 are formed in the casing between the slots 40 and 41 for removing extracted nails.

When starting, the movable elements of the apparatus are positioned as shown in Figure l, in that pressure air is supplied to the underside of the plunger to hold it in its uppermost position. The upward movement of the plunger and its rod is limited in that the projecting portion 26 of one disk engages the upper edge of the slot 41. At the same time the projecting end of the locking member is limited by the upper edge of the slot 40 to engage in turn the projecting portion of the other disk. As seen in Figures 1, 3 and 4, the slot 40 extends somewhat further upwards than the slot 41. Thus, the two jawstwill be removed from each other and in a certain position the notch 27 in the foremost disk in Figure 1 is situatedexactly beside a notch in the other (rear) disk, and hereby the hook 31 of the locking member snaps into the two notches to keep the jaws in open position until the locking member is actuated in opposite direction. In the position shown in Figure 3, pressure air has been supplied to the upper side of the plunger 10 by depressing the knob 18, so that the piston rod 11 has been moved downwardly. When the points of the jaws pass the bottom wall of the casing 38 to grip the head of a nail, the extended portion of the locking member 29 engages an abutment 43 in the lower portion of the slot 40, so that the locking lever is rocked and the hook 3l is released from its locking engagement. Immediately thereafter the projecting elements 26 of the disks 22 engage the lower edges of the slots 40, 41 with the result that the jaws are approached to each other, when the piston rod continues to move outwards. The circular outer curvature of the jaws facilitates considerably the application of the grip. Finally, when the jaws have reached the position gripping the head of the nail, as shown in Figure 4, the notch 28 in the foremost disk 22 is situated exactly beside a notch in the rear disk, whereby the hook 32 snaps into said notches and locks the jaws in gripping position. This gripping position is maintained, while the nail is extracted by releasing the valve knob 18. When the plunger 10 has returned to the position shown in Figure l, the jaws are opened, as described above, and the nail drops out. The operation described may then be repeated immediately. a

What I claim is:

1. A pneumatic spike extractor, comprising a cylinder, a piston therein, means for alternately connecting the cylinder chambers on both sides of the piston with a source of pressure gas, a piston rod connected to said piston projecting through one end of said cylinder, fixed abutments adjacent the end positions of said piston rod, two jaws pivotably mounted on the outer end of said rod having locking members thereon, a double-armed lever pivotably mounted on said piston rod and rockable between two end positions by engaging said fixed abutments, locking members provided on said lever at both sides of its pivot to cooperate with said locking members on said jaws to lock the jaws in open and gripping position respectively when said rod is retracted and protruded respectively.

2. A pneumatic spike extractor, comprising a cylinder, a piston therein, means for alternately connecting the cylinder chambers on both sides of the piston with a source of pressure gas, a piston rod connected to said piston projecting through one end of said cylinder, fixed abutrnents adjacent the end positions of said piston rod, two jaws pivotably mounted on the outer end of said rod having locking members thereon, a double-armed lever pivotably mounted on said piston rod and rockable between two end positions by engaging said fixed abutments, locking members provided on said lever at both sides of its pivot to cooperate with said locking members on said jaws to lock the jaws in open and gripping position respectively when said rod is retracted and protruded respectively, and a spring member arranged to actuate the lever to retain it in either of its locking end positions.

3. A pneumatic spike extractor, comprising a cylinder, a piston therein, means for alternately connecting the cylinder chambers on both sides of the piston with a source of pressure gas, a piston rod connected to the piston projecting through one end of the cylinder, fixed abutments adjacent the end positions of said piston rod, two jaws pivotably mounted on the outer end of said rod having locking recesses therein, a double-armed lever pivotably mounted on the piston rod rockable between two end positions by engaging said fixed abutments, hooks provided on said lever at both sides of its pivot to cooperate with said recesses in the jaws to lock the jaws in open and gripping position respectively when the rod is retracted and protruded respectively and a spring member arranged to actuate said lever to retain it in either 0 its locking end positions.

References Cited in the file of this patent UNITED STATES PATENTS 

